The applicant claims and requests a foreign priority, through the Paris Convention for the Protection of Industry Property, based on a utility model application filed in the Republic of Korea (South Korea) with the filing date of Sep. 25, 2001, with the utility model application number 10-2000-0032507, by the applicant. (See the attached declaration)
The invention relates to an artificial heart for a patient requiring a cardiopulmonary life support in form of either artificial heart implantation or extracorporeal heart assistance. More specifically, the present invention relates to a cardiopulmonary life support system that substantially prevents blood clotting (thrombus) and dissolution or destruction of red blood cells (hemolysis) from occurring in blood vessels of a heart patient who receives its assistance.
FIG. 1 is a schematic view showing a heart 2, lungs 4 and a blood circulation in a mammal or a human, wherein arrows indicate direction of the blood circulation. As shown therein, the heart 2 includes two atriums above and two ventricles below. A main vein 6 is connected to the right atrium and the right ventricle is linked to a pulmonary artery 8. The lungs are connected to the left atrium and the left ventricle is linked to an aorta 10. Regular pumping of the left ventricle pushes out blood therein into the aorta 10 to deliver nutrition and oxygen to each capillary vessel in the body. Meanwhile, the blood with less oxygen is in turn collected in the main vein that links to the right atrium to complete a blood circulation known as a systematic circulation. The oxygen-depleted blood collected in the right atrium is released down to the right ventricle and sent to each lung through the pulmonary artery for blood oxygenation. The blood oxygenated in the lungs is released through the left atrium down to the left ventricle. Through the blood circulation for blood oxygenation also known as a pulmonary circulation, the oxygen-depleted blood is converted to an oxygen-rich blood and collected back in the left ventricle. The oxygen-rich blood collected in the left ventricle repeats the systematic circulation in accordance with the regular pumping which generates rhythmic pulses. A valve in each atrium and ventricle serves to prevent a reverse stream.
Each rhythmic pulse in the atriums and ventricles differs depending on age, sex and physical condition. However, the heart pulse frequency for an individual is regular in a stabilized condition. A standard per-minute heart pulse frequency is known to range about 100 to 140 for infants, 80 to 90 for elementary school kids, 60 to 80 for young and middle aged adults, and 60 to 70 for senior people. Male tends to be less in pulse frequency than female. In general, the smaller the body, the more frequent becomes the heart pulsation for animals. If the body-surface area is larger than the body volume, heat emission becomes further invigorated and thus blood circulation should be faster to complement the loss resulting from the heat emission. For example, the per-minute pulse frequency ranges about 30 to 40 for elephants, 90 to 90 for dogs, 140 to 160 for rabbits, and 200 to 300 for rats. The pulse frequency in an artificial heart can be adjusted by controlling the rotation of a motor that drives the artificial heart.
The heart along with lungs is the most crucial organ that allows a living body to maintain its life. However, the heart should remain motionless and emptied in order to conduct a precise surgical heart operation. Therefore, considering the vitality of the heart without which the life does not last more than five minutes, an artificial heart or cardiopulmonary assistance device should be inevitably utilized in such life threatening urgent circumstances as a heart attack, a sepsis related shock, or a myocardium infraction.
Many studies on artificial hearts have been focused on blood pumping which most affects functioning of an artificial heart in a body. The leading conventional arts regarding artificial hearts will be now briefly described focusing each function of blood pumping.
FIG. 2 is a view showing a conventional cardiopulmonary device using a rotary pump. As shown therein the rotary pumping device includes a blood storage, a rotary type pump 12, an oxygenator 13, and a flexible tube 14. The blood storage 11 stores therein a blood from a main vein of a patient. The rotary blood pump 12 serves to transfer the blood from the storage 11 to the oxygenator 13. The flexible tube 14 links the blood storage 12 and the oxygenator 13. The flexible blood tube 14 is arc-bent by 90 degrees around the rotary blood pump 12. A rotation shaft 15 is radially formed from the arc-bent portion of the tube 14 through the center of the rotary pump 12. A rotation arm 16 is engaged to the rotation shaft 15 and two rotary rollers 17 are rotatably provided to rotate in accordance with the rotation shaft 15. The rotation of the shaft 15 allows the pump 12 to serve to make a sequential squeezing rotation along the arc-bent portion of the tube 14. However, the squeezing rotation of the pump 12 fails to generate a stable, pulsatile blood pumping. Further, the excessive pressure for the squeezing rotation tends to easily lead to thrombosis and hemolysis in the oxygenator 13. Also, the rotary pump 12 is only usable for about 6 to 8 hours which substantially limits its application to a time taking surgical heart operation.
FIG. 3 shows a schematic cross-sectional view of a conventional centrifugal blood pump 21. The centrifugal blood pump 21 includes an input port (not shown) to receive blood from a flexible tube (not shown) connected to a right atrium, an output port 22 to release the blood from the blood pump 21, and an impeller 23 having blades. The rotation speed of the impeller 23 can be adjusted depending on a patient. However, since the blood in the centrifugal blood pump 21 becomes in contact with either the inner surface of the blood bump 21 or mechanical surfaces of the impeller 23, there may easily occur blood clotting or blood dissolution.
In particular, the damage incurrence on red blood cells or blood platelets due to the blood clotting and dissolution is determined by stress resulting from the blood flow in the pump 21 and by how long the blood has stayed in the pump 21. Also, the stress due to the blood flow is determined by the rotation speed of the impeller 23 and by the asperity of the mechanical surfaces, thereby increasing possibility of blood damage. The time period in which the blood stays in the centrifugal blood pump 21 is a major factor to consider in the pump design. A shear stress sufficient to affect the blood staying in the pump may lead to thrombosis resulting from congelation, embolism or fibrin accumulation on the inner surface of the pump. There may also occur blood dissolution or red cell destruction due to a flow separation, a cavitation, or a solution swirl which may be caused by the rotation of the impeller 22. Therefore, the centrifugal blood pump 21 can be utilized for a limited time period like the rotary blood pump.
FIG. 4 shows a conventional pulsatile blood pump 31. As shown therein, the pulsatile pump 31 includes a bag tube 32, a pressure plate 33, a plate support 34, a rotation body 35, and a drive motor 36. The bag tube 32 is provided with a valve (not shown) at each end thereof. The pressure plate 33 pressurizes the tube 32 for blood transfer. The plate support 34 supports and vertically shuttles the pressure plate 33. The rotation body 35 is threaded to allow the plate support 34 to make a vertical reciprocal movement.
When the pressure plate 33 the plate support 34 are lowered according to the rotation body 35 driven by the motor 36, the blood is discharged from the tube 32, and when raised the blood is supplied into the tube 32, thereby enabling the pulsatile blood pumping. However, the pulsatile blood pump 31 may cause friction by the contact of the rotation body and the plate support 34 to thereby undermine a stabilized reciprocal movement. Further, the reciprocal rotation of the drive motor 36 that drives the rotation body 35 may increase pressure for pumping the blood to the oxygenator, thereby incurring thrombosis and hemolysis.
FIG. 5 shows a conventional dual pulsatile blood pump 41. As shown therein, the pulsatile pump 41 includes input ports 43, 43xe2x80x2, output ports 44, 44xe2x80x2, input valves 45, 45xe2x80x2, and output valves 46, 46xe2x80x2. Each valve is formed in a corresponding one of the ports. The pump 41 also includes a pump case 42 that houses therein a spherical body 52. The spherical body 52 has a groove 50 therearound and a gear 51. The gear 51 is engaged to a rack 53 attached to an inner wall of the pump case 42. A rubber membrane 49, 49xe2x80x2 covers the gear 51, rack 53 and the groove 50. A belt 54 is carried in along the groove 50 of the body 52 and around a pulley 57 linked to a motor 56. A tension applied to the pulley 57 together with the engagement of the gear 51 and the rack 53 enables a shuttling movement of the spherical body 52, whereby the body 52 makes a horizontal shuttle movement to pump the blood in the blood chamber 48. The dual pulsatile blood pump 31 substantially decreases thrombosis and hemolysis compared to the rotary pump or other pulsatile pumps. However, the mechanical surfaces are exposed to the blood except for the rubber membranes 49, 49xe2x80x2 and the input and output ports are also exposed to mechanical surfaces, which may still incur thrombosis and hemolysis. Further, the streamline formation around the input and output ports in the pump chamber 48, 48xe2x80x2 may lead to pressure loss which easily results in blood clotting or blood dissolution. In addition, the continued friction and stress may serve to elongate the belt and this makes it difficult to maintain stable pulsation and blood pressure. Also, the conventional dual pulsatile blood pump 41 substantially increases production cost due to mechanical requirements for the shuttle movement of the spherical body 41.
The invention is contrived to overcome the conventional disadvantages. Accordingly, an object of the present invention is to provide a cardiopulmonary life support system that substantially prevents blood clotting (thrombosis) and dissolution or destruction of red blood cells (hemolysis) from occurring in blood vessels of a heart patient who receives its assistance.
Another object of the invention is to enable a heart patient to use the life support system for a longer time period in form of either extracorporeal life support or surgical implantation. A further object is to improve portability for an extracorporeal system application and to minimize the size of the life support system to facilitate implantation. A still further object is to realize a rhythmic pulsation substantially equivalent to the systematic pulsation in a living body.
To achieve the above-described objects, the cardiopulmonary life support system according to the present invention comprises a housing defined by a top side, a bottom, a rear side, and an inner periphery. First and second tubes are adjacent to each other in the housing, and the first and second tubes each have an input port and an output port. An alternating member is attached to the housing and disposed between the first and second tubes. The alternating member alternately squeezes the first and second tubes.
In an embodiment, the life support system further comprises a valve formed in said each input and output port to prevent a reverse stream in the first and second tubes, and an oxygenator connected to the output port of the first tube and the input port of the second tube to convert an oxygen-depleted blood to an oxygen-rich blood.
For a better performance, there may be further provided first and second blood storages. The first blood storage is formed between the oxygenator and the input port of the first tube to temporarily store therein the oxygen-rich blood oxygenated in the oxygenator. The second blood storage is connected to the output port of the second tube to temporarily store therein the oxygen-depleted blood.
In this construction, an initial squeezing of the alternating member on the first tube enables the oxygen-rich blood to partially pump out from the first tube through the first tube output port. A subsequent squeezing of the alternating member on the second tube enables the oxygen-depleted blood to partially pump out from the second tube through the second output port while a restoration of the first tube to its original shape enables the first tube to suck in as much as pumped out therefrom through the first input port valve. A further subsequent squeezing of the alternating member on the first tube enables the oxygen-rich blood to partially pump out from the first tube through the first output port while a subsequent restoration of the second tube to its original shaft enables the second tube to suck in as much as pumped out therefrom through the second input port valve.
The advantages of the cardiopulmonary life support system according to the present invention are numerous. Initially, the gently alternating reciprocal movement of the alternating member squeezes the first and second tubes sequentially, alternately, gently and efficiently for blood pumping operation so that the oxygenator becomes less pressurized by the repeated blood pumping, thereby substantially decreasing incurrence of blood clotting (thrombosis) and dissolution or destruction of red blood cells (hemolysis), which are known as common side effects to most patients receiving assistance of conventional artificial hearts.
Further, the first and second tubes are formed of a flexible, resilient material and the solid alternating member is operatively provided between the first and second tubes in such a simplified, stabilized construction that the expected life span of the life support system is substantially extended without system replacement. In addition, the alternating member and the first and second tubes are efficiently accommodated within the housing to alternately enable each blood pumping operation for the first and second tube in such a limited space that a significant system size decrease is realized, for example, from a conventional refrigerator size to a palm size in an implantation version of the present invention or to a portable size in an extracorporeal assistance version of the present invention.
Also, the gentle, pulsatile blood pumping operation accomplished within the housing in systematic combination of the flexible blood tubes and the gently alternating solid member generates safe and steady blood pulses substantially similar to those of a natural heart, thereby improving product reliability. More importantly, the artificial blood pumping system adapting the alternately tube-squeezing mechanism requires less elements and further simplifies the overall structure for the blood pumping operation, thereby substantially decreasing production cost, whereby a surgical implantation of the life support system may be realized, for example, within about one and half times the medical bill charged for a large surgical heart operation.
Although the present invention is briefly summarized, the fuller understanding of the invention can be obtained by the following drawings, detailed description and appended claims.